1. Field of the Invention
This invention relates to a method of and apparatus for classifying, separating and assorting particles. More particularly, the invention involves combinations of separations to segregate particles having like physical characteristics from a mixture of particles having various physical characteristics.
2. Description of the Prior Art
Shaking tables have been used for segregating particles according to physical characteristics by simultaneous separating actions that include standard and reverse classification by size and stratification according to specific gravity. Examples of such shaking tables are shown in U.S. Pat. Nos. 1,044,067; 1,315,880 and 1,999,000. While such shaking tables provide a rough, crude or limited separation, it has been necessary to sift certain material through screens after such segregation by the shaking tables to achieve a finish degree of separation. Screening is difficult to perform continuously because retained particles block the screen and necessitate frequent interruptions in the separation operation. Separation by screening is most effective when there is but a small quantity of material having a size approximately the same as any one sieve size although the material screened can vary over a wide range of sizes. Shaking tables operate more effectively when all of the particles are nearly the same size, and the size range of material that can be treated is therefore smaller for shaking tables than for screens.
A finish or fine degree of separation is also difficult to achieve with shaking tables because particles of different classification are often re-mixed upon removal from a stratified bed. Normally, the planes of stratification are substantially horizontal and the order of classification is along a vertical axis. The uppermost particle stratum must be skimmed or scalped from the lower particle strata, and, unless the plane of removal coincides with the plan of strata separation, particles from more than one stratum will be mixed. For continuous operation, removal is usually achieved by gravitational flow down a plane inclined relative to the horizontal or by vibratory feeding of the material along an inclined plane; in using this procedure different classes of particles are mixed to some extent because they are removed from more than one stratum at a time.